Method for continuously producing artificial marble and apparatus therefor

ABSTRACT

Disclosed are a method and an apparatus for continuously producing an artificial marble plate capable of simultaneously and uniformly hardening a raw material compound for an artificial marble plate, preventing the warpage of the artificial marble plate, and improving heat transmission efficiency and productivity. The apparatus includes upper and lower carrier films facing each other and receiving a raw material compound for the artificial marble plate into a gap therebetween; upper and lower horizontal heating plates, each including temperature controlling means and heating means for heating upper and lower surfaces of the raw material compound at the same temperature by the same heat transmission manner to harden the raw material compound, while the upper and lower carrier films moving along a gap between the upper and lower horizontal heating plates; and a pair of gaskets disposed at horizontal edges of the upper and lower carrier films for regulating thickness and width of the artificial marble plate obtained by hardening the raw material compound.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and an apparatus forcontinuously producing an artificial marble plate with a constantthickness.

[0003] 2. Description of the Related Art

[0004] As exemplary apparatuses for producing a hardened polymer plateby continuously polymerizing compounds, Japanese Patent Laid-open No.Hei 10-217264 discloses “a method and an apparatus for continuouslyproducing an artificial marble palate made of acrylate resin”, andJapanese Patent Laid-open No. 2000-317957 discloses “a method and anapparatus for producing an artificial marble plate”.

[0005]FIG. 1 is a cross-sectional view of the continuous hardeningapparatus disclosed by Japanese Patent Laid-open No. Hei 10-217264. Thecontinuous hardening apparatus comprises a pair of endless steel belts101, an idle pulley 102 serving as miscellaneous equipment thereof, adriving pulley 102′, upper and lower film feed units 103 and 104, a rawmaterial compound feed unit 105, a thickness adjusting unit 106,hardening chambers 107, 108, 109 and 110, nozzle units 111 and 111′, adriving motor 112, and belt back-up rolls 113 and 113′. This apparatusis characterized in that a polymerized raw material compound for anartificial marble plate is continuously entered into the apparatus andthen continuously hardened by means of the movement of the belts 101,thus producing a platy artificial marble semi-product, and the producedsemi-product is produced as a final artificial marble plate by anedge-trimming step and a surface-polishing step. Here, each of thehardening chambers 107, 108, 109 and 110 is divided into two or moreareas, and each of the divided areas includes an air-circulating unithaving a blower, a heater, a circulating duct and a nozzle unit. The twodivided areas of each of the hardening chambers 107, 108, 109 and 110are symmetrically installed on the upper and lower surfaces of one pairof the endless steel belts 101 provided with the raw material compoundstacked thereon, and provides a hot blast required to produce the finalproduct by hardening the raw material compound, thus heating and coolingthe upper and lower surfaces of the polymerized raw material compound.

[0006] The hot blast is transmitted into the raw material compound viathe air-circulating units symmetrically installed on the upper and lowersurfaces of the endless steel belts 101, thereby hardening the rawmaterial compound. In this case, the heat from the hot blast (that issupplied from the air-circulating units disposed on the upper surface ofthe endless steel belts 101) is transmitted to the upper surface of theraw material compound by convection, while the heat from the hot blast(that is supplied from the air-circulating units disposed on the lowersurface of the endless steel belts 101) is transmitted to the lowersurface of the raw material compound by conduction since the hot blastis first transmitted to the endless steel belt and then to the rawmaterial compound.

[0007] That is, since the technique disclosed by Japanese PatentLaid-open No. Hei 10-217264 applies different heat transmission mannersto the upper and lower surfaces of the raw material compound, it isdifficult to supply heat in the same amount to the upper and lowersurfaces of the raw material compound, thus causing a warpage (stresstorsion) on the artificial marble plate obtained by hardening the rawmaterial compound.

[0008]FIG. 2 is a cross-sectional view of the apparatus for producing anartificial marble plate disclosed by Japanese Patent Laid-open No.2000-317957. This apparatus comprises endless belts 201 and 201′, rotarydrums 202, 202′, 203 and 203′, rollers 204 and 204′, a metering pump 205for feeding a raw material 205, a raw material injection unit 206,gaskets 207 and 207′, hot water spray units 208 and 208′, second heatingzones 209 and 209′, cooling zones 210 and 211, a belt driving motor 212,a first heating zone 213, heating units 214 and 214′, and a producedartificial marble plate 215. The apparatus of this patent uses two pairsof the endless belts 201 and 201′, and employs a hardening method inwhich a polymerized raw material for an artificial marble plate ishardened by spraying hot water to each of the endless belts 201 and201′. Since the heat transmission to the upper and lower surfaces of thepolymerized raw material compound is performed by the same manner, thishardening method prevents the warpage of the artificial marble plateobtained by hardening the raw material compound. However, the abovehardening method requires a plurality of heating zones and coolingzones, thus complicating the structure of the apparatus itself.

[0009] Further, the above-described two apparatuses shown in FIGS. 1 and2 must be large-sized so as to control the tensions of the one pair ortwo pairs of the steel belts and operate the steel belts.

SUMMARY OF THE INVENTION

[0010] Therefore, the present invention provides an apparatus and amethod for continuously producing an artificial marble plate withoutwarpage, in which a raw material compound for the artificial marbleplate is continuously fed to a gap between upper and lower horizontalheating plates, and upper and lower surfaces of the raw materialcompound are hardened at the same temperature by the same heattransmission manner, i.e., conduction. Thus, the hardening is performedon the upper and lower surfaces of the raw material compound at the samerate, thereby increasing the productivity of the apparatus.

[0011] In accordance with one aspect of the present invention, anapparatus for continuously producing an artificial marble platecomprises upper and lower carrier films facing each other and receivinga raw material compound for the artificial marble plate into a gaptherebetween; upper and lower horizontal heating plates, each includingtemperature controlling means and heating means for heating upper andlower surfaces of the raw material compound at the same temperature bythe same heat transmission manner to harden the raw material compound,while the upper and lower carrier films moving along a gap between theupper and lower horizontal heating plates; and a pair of gasketsdisposed at horizontal edges of the upper and lower carrier films forregulating thickness and width of the artificial marble plate obtainedby hardening the raw material compound.

[0012] The apparatus may further comprise upper and lower carrier filmfeed unwinders for feeding the upper and lower carrier films to the gapbetween the upper and the lower horizontal heating plates; a rawmaterial feed tank for feeding the raw material compound for theartificial marble plate into the gap between the upper and lower carrierfilms; a raw material overflow prevention block, disposed between theraw material feed tank and the lower horizontal heating plate, forpreventing the raw material compound fed from the raw material feed tankfrom flowing over the gaskets; a contact roll, disposed after the rawmaterial overflow prevention block and before the upper horizontalheating plate, for bringing the upper carrier film into contact with theraw material compound; a gasket-protecting film surrounding the gasketsto protect the gaskets; gasket fixing members and a gasket fixing frame,disposed over the gaskets, for fixing the gaskets; vertically movablecylinders, disposed on the upper horizontal heating plate, forcontrolling the height of the upper horizontal heating plate; upper andlower carrier film recovery winders, communicated with end parts of theupper and lower horizontal heating plates, for collecting the upper andlower carrier films from the artificial marble plate; and a cuttingunit, communicated with the upper and lower carrier film recoverywinders, for cutting the artificial marble plate released from the upperand lower carrier films.

[0013] The apparatus may further comprise a carrier film fixture,disposed under the upper carrier film and on the lower carrier film, forfixing the upper and lower carrier films, for fixing the upper and lowercarrier films. The carrier film fixture may include a clamping pin; achain belt for fixing the clamping pin; a position adjusting gear foradjusting the position of the chain belt; and a driving gear for drivingthe chain belt.

[0014] The heating means may be one unit selected from the groupconsisting of a hot water heater, a steam heater, and an electric heaterunit. Further, preferably, the heating means may heat the raw materialcompound at a temperature in the range of 30 to 100° C. In case that theheating temperature is excessively low, the time taken to harden the rawmaterial compound is increased and the productivity of the artificialmarble plate is lowered. In case that the heating temperature isexcessively high, the raw material compound is undesirably suddenlyhardened.

[0015] The outer diameter or the height of each of the gaskets may bepreferably 6 to 40 mm, and more preferably 6 to 20 mm according to thethickness of the artificial marble plate to be produced. Each of thegaskets may be made of one material selected from the group consistingof polymer such as Teflon, nylon and rubber, and metal such as stainlesssteel, aluminum and copper. Further, each of the gaskets may be made ofa circle-shaped or square-shaped tube or pipe. Furthermore, one pair ofthe gaskets may be spaced from each other by a distance of 500 to 1,300mm. For instance, in case that the width of the artificial marble plateto be produced is in the range of 760 to 1,220 mm, the distance betweenthe gaskets may be in the range of 800 to 1,300 mm.

[0016] Each of the upper and lower carrier films may be made of one ormore materials selected from the group consisting of polyethylene,polyester, polypropylene and polyvinyl alcohol. Preferably, each of theupper and lower carrier films may have a thickness of 20 to 100 μm. Incase that the upper and lower carrier films are excessively thin, thefilms are easily tom or cannot transfer the raw material compoundthereon. In case that the upper and lower carrier films are excessivelythick, since the films are undesirably wrinkled, it is difficult tomaintain the smoothness of the upper surfaces of the films in thehardening of the raw material compound.

[0017] The vertically movable cylinders for controlling the height ofthe upper horizontal heating plate may be vertically moved by a distanceof 0 to 1,000 mm. For instance, the movement distance of the verticallymovable cylinders may be controlled in the range of 6 to 20 mm accordingto the thickness of the artificial marble plate to be produced duringthe producing process, and in the range of 300 to 1,000 mm when theapparatus is cleaned up after a production run or during repair work.

[0018] In accordance with another aspect of the present invention, thereis provided a method for continuously producing an artificial marbleplate. The method comprises: feeding a raw material compound for theartificial marble plate to a space defined by upper and lower carrierfilms facing each other and a pair of gaskets disposed at horizontaledges of the upper and lower carrier films; and heating upper and lowersurfaces of the raw material compound at the same temperature by thesame heat transmission manner to harden the upper and lower surfaces ofthe raw material compound at the same rate, via a pair of upper andlower horizontal heating plates, while moving the upper and lowercarrier films along a gap between the upper and lower horizontal heatingplates.

[0019] The raw material compound includes one or more thermosettingresins selected from the group consisting of unsaturated polyesterresin, acrylate resin and methacrylate resin, one or more fillersselected from the group consisting of aluminum hydroxide, calciumcarbonate, silicate and magnesium oxide, one or more reaction initiatorsselected from the group consisting of peroxide compound and perestercompound, and acrylate compound as a crosslinking agent.

[0020] The raw material compound for the artificial marble plate mayhave a viscosity of 10 to 300 poise. In case that the viscosity of theraw material compound is excessively low, severe phase separation of theraw material compound occurs, thus deforming the artificial marbleplate. In case that the viscosity of the raw material compound isexcessively high, it is difficult to smoothly feed the raw materialcompound or easily remove air from the fed raw material compound. Inexemplary embodiments of the invention, the raw material compound forthe artificial marble plate may have a viscosity of 50 to 150 poise.

[0021] The upper horizontal heating plate may be located 0.5 to 1.0 mmabove the gaskets, in consideration of the difficulty in moving theupper carrier film due to the friction on the interfaces between theupper horizontal heating plate and the thickness regulating gaskets.

[0022] In accordance with the apparatus and method for continuouslyproducing an artificial marble plate of the present invention, the upperand lower horizontal heating plates with a temperature controlled in therange of 30 to 100° C. are symmetrically disposed on the upper and lowersurfaces of the raw material compound, a gap between the upper and lowerhorizontal heating plates is controlled in the range of 0 to 1,000 mm,and the lower surface of the raw material compound contacts the uppersurface of the lower horizontal heating plate and the upper surface ofthe raw material compound contacts the lower surface of the upperhorizontal heating plate. Accordingly, since heat is transmitted to theupper and lower surfaces of the raw material compound by the samemanner, it is possible to produce an artificial marble plate withoutwarpage.

[0023] In accordance with the method for continuously producing anartificial marble plate of the present invention, the upper and lowerhorizontal heating plates, which have a temperature controlled in therange of 30 to 100° C. horizontally and face each other, are disposed tohave a gap between the upper and lower horizontal heating plates in therange of 0 to 1,000 mm, and a lower carrier film with a thickness of 20to 100 μm, made of one or more materials selected from the groupconsisting of polyethylene, polyester, polypropylene and polyvinyl,alcohol, is disposed on the upper surface of the lower horizontalheating plate so that the lower carrier film is continuously movedbetween the upper and lower horizontal heating plates. The raw materialcompound to be polymerized is disposed on the lower carrier film, andthen an upper carrier film with a thickness of 20 to 100 μm, made of oneor more materials selected from the group consisting of polyethylene,polyester, polypropylene and polyvinyl alcohol, is disposed on the uppersurface of the raw material compound. The upper carrier film contactsthe lower surface of the upper horizontal heating plate so that theupper carrier film is continuously moved between the upper and lowerhorizontal heating plates. Accordingly, the artificial marble plate isobtained by hardening the raw material compound.

[0024] It is advantageous to use the upper and lower carrier filmscontacting the upper and lower surfaces of the raw material compoundmade of the same material with the same thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

[0026]FIG. 1 is a cross-sectional view of an apparatus disclosed byJapanese Patent Laid-open No. Hei 10-217264;

[0027]FIG. 2 is a cross-sectional view of an apparatus disclosed byJapanese Patent Laid-open No. 2000-317957;

[0028]FIG. 3 is a perspective view of an apparatus for continuouslyproducing an artificial marble plate in accordance with an exemplaryembodiment of the present invention;

[0029]FIG. 4 is a cross-sectional view taken along the line A-A′ of FIG.3;

[0030]FIG. 5 is a cross-sectional view taken along the line B-B′ of FIG.3;

[0031]FIG. 6 is a schematic view of a carrier film fixture in FIGS. 4and 5;

[0032]FIG. 7 is a schematic plan view of a pin fixing chain belt of FIG.6; and

[0033]FIG. 8 is a diagram illustrating a final product produced by theapparatus of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] Now, preferred embodiments of the present invention will bedescribed in detail with reference to the annexed drawings.

[0035]FIG. 1 is a cross-sectional view of a conventional apparatus forcontinuously producing an artificial marble plate, which is providedwith a pair of endless steel belts, disclosed by Japanese PatentLaid-open No. Hei 10-217264. FIG. 2 is a cross-sectional view of aconventional apparatus for continuously producing an artificial marbleplate, which is provided with two pairs of endless belts, disclosed byJapanese Patent Laid-open No. 2000-317957. As described above, theconventional apparatus of FIG. 1 applies different heat transmissionmanners to the upper and lower surfaces of a raw material compound, thuscausing a warpage on the produced artificial marble plate. Further, theconventional apparatus of FIG. 2 has a complicated structure.

[0036]FIG. 3 is a perspective view of an apparatus for continuouslyproducing an artificial marble plate in accordance with an exemplaryembodiment of the present invention. A lower carrier film 1 has athickness of approximately 20 to 100 μm, and may be made ofpolyethylene, polyester, polypropylene, polyvinyl alcohol, etc.

[0037] An upper carrier film 2 has the same thickness as that of thelower carrier film 1, and is made of the same material as that of thelower carrier film 1. Preferably, the upper and lower carrier films 1and 2 are made of the same material with the same thickness. Morepreferably, the upper and lower carrier films 1 and 2 are made ofpolyvinyl alcohol with a thickness of 35 to 70 μm.

[0038] The upper and lower carrier films 1 and 2 are fed to a gapbetween upper and lower horizontal heating plates 10 and 11 by upper andlower carrier film feed unwinders 1-1 and 2-1.

[0039] A pair of right and left thickness regulating gaskets 4 isprovided at horizontal edges of the upper and lower carrier films 1 and2 to regulate the thickness and width of an artificial marble plate tobe produced. The thickness regulating gaskets 4 are made of a polymerictube with an outer diameter of 6 mm to 40 mm such as a Teflon tube ornylon tube, a metal pipe with an outer diameter of 6 mm to 40 mm such asa stainless steel pipe, an aluminum pipe or a copper pipe, or asquare-shaped material with a height of 6 mm to 40 mm such as Teflon,nylon, rubber, stainless steel, aluminum, copper, etc. Preferably, thethickness regulating gaskets 4 are made of a Teflon tube or a nylon tubewith an outer diameter of 6 mm to 30 mm. Each of the right and leftthickness regulating gaskets 4 is respectively fixed to thicknessregulating gasket fixing frames 3 and 3′ disposed over the thicknessregulating gaskets 4.

[0040] A raw material feed tank 6 serves to feed a raw material forproducing the artificial marble plate. A raw material overflowprevention block 5 is disposed between the raw material feed tank 6 andthe lower horizontal heating plate 11 to prevent the raw materialcompound from flowing over the thickness regulating gaskets 4.Preferably, the raw material overflow prevention block 5 is made of amaterial with high tolerance to methyl methacrylate monomer and styrenemonomer. The raw material overflow prevention block 5, for instance,includes stainless steel or Teflon, however, the raw material overflowprevention block 5 may be made other materials if a layer with a hightolerance to solvents is formed on the surface of the raw materialoverflow prevention block 5 contacting the raw material compound.

[0041] An upper carrier film contact roll 7, which is disposed after thematerial overflow prevention block and before the upper horizontalheating plate, brings the upper carrier film 2 into contact with theupper surface of the raw material compound so that the raw materialcompound is protected from foreign substances such as air and dust. Theupper carrier film contact roll 7 serves to control the thickness of theartificial marble plate to be produced.

[0042] Vertically movable cylinders 9 are disposed on the upperhorizontal heating plate 10 to control the height of the upperhorizontal heating plate 10, and move upward and downward so as tosufficiently elevate the upper horizontal heating plate 10 for repairingor cleaning.

[0043] The upper horizontal heating plate 10 functions to supply heat tothe raw material compound and control the thickness of the fed rawmaterial compound, and includes a steam or hot water feed unit or anelectric heater unit as heating means. Here, the heating temperature ofthe heating means of the upper horizontal heating plate 10 can becontrolled in the range of approximately 30 to 100° C.

[0044] The lower horizontal heating plate 11 serves to support the lowercarrier film 1, prevents the raw material compound from sagging duringproduction, and supplies heat to the raw material compound so that theraw material compound is continuously hardened. Similarly to the upperhorizontal heating plate 10, the lower horizontal heating plate 11includes a steam or hot water feed unit or an electric heater unit asheating means. Further, the heating temperature of the heating means ofthe lower horizontal heating plate 11 can be controlled in the range ofapproximately 30 to 100° C. Particularly, it is important to heat theupper and lower surfaces of the raw material compound at the sametemperature using the upper and lower heating plates 10 and 11.

[0045] A lower horizontal heating plate supporting frame 12 is providedto support the lower horizontal heating plate 11. Upper and lowercarrier film recovery winders 15 and 16 are disposed the end areas ofthe upper and lower horizontal heating plates 10 and 11 to collect theupper and lower carrier films 1 and 2 from the upper and lower surfacesof the artificial marble plate obtained by hardening the compound bymeans of the upper and lower horizontal heating plates 10 and 11.

[0046] A cutting unit 17 is a circular saw communicated to the upper andlower horizontal heating plates 10 and 11, and serves to continuouslycut the artificial marble plate into plural units with a regulated size.

[0047]FIG. 4 is a cross-sectional view taken along the line A-A′ of astarting area of the lower horizontal heating plate 11 of FIG. 3.Thickness regulating gasket fixing members 3-1 are disposed on thethickness regulating gasket fixing frames 3 and 3′, and holds and fixesthe thickness regulating gaskets 4 for regulating the thickness andwidth of a final product to the thickness regulating gasket fixingframes 3 and 3′. A supporting frame 14 is provided to support the upperhorizontal heating plate 10 and the vertically movable cylinders 9.

[0048]FIG. 5 is a cross-sectional view taken along the line B-B′ of FIG.3. A thickness regulating gasket-protecting film 8 surrounds thethickness regulating gaskets 4 to prevent the raw material compound fromcontacting the thickness regulating gaskets 4, thus protecting the rawmaterial compound from damage. The thickness regulatinggasket-protecting film 8 has a thickness of 10 to 10 μm, and is made ofpolyethylene, polyester, polypropylene, or polyvinyl alcohol.

[0049]FIG. 6 is a schematic view of a carrier film fixture 13 in FIGS. 4and 5. The carrier film fixture 13 is disposed under the upper carrierfilm 2 and on the lower carrier film 1 to fix the upper and lowercarrier films 2 and 1. The carrier film fixture 13 comprises a clampingpin 13-1, a pin fixing chain belt 13-2 for fixing the clamping pin 13-1,a chain belt position adjusting gear 13-3 for adjusting the position ofthe pin fixing chain belt 13-2, and a chain belt driving gear 13-4 fordriving the pin fixing chain belt 13-2 so that the upper and lowercarrier films 1 and 2 are continuously transferred by the chain beltdriving gear 13-4.

[0050]FIG. 7 is a plan view of the pin fixing chain belt 13-2 of FIG. 6,and shows the positions of the upper and lower carrier films 1 and 2 onthe upper and lower surfaces of the pin fixing chain belt 13-2. FIG. 8shows an artificial marble plate produced by the apparatus of thepresent invention.

[0051] Hereinafter, with reference to FIG. 3, a method for continuouslyproducing an artificial marble plate in accordance with the presentinvention will be described in detail.

[0052] First, there is prepared a raw material compound by mixing athermosetting resin such as unsaturated ester resin, acrylate resin ormethacrylate resin, a filler such as aluminum hydroxide, silicate ormagnesium oxide, a reaction initiator such as peroxide compound orperester compound, and a crosslinking agent such as acrylate compound.The raw material compound has a viscosity of 10 to 300 poise, preferably30 to 200 poise, and more preferably 50 to 150 poise. Here, theviscosity of the raw material compound is adjusted by controlling theratio of the thermosetting resin and the filler, and controlling thecontents of monomers and polymers contained in the thermosetting resin.

[0053] The thickness regulating gaskets 4 are set on the thicknessregulating gasket fixing members 3-1, and fixed to the thicknessregulating gasket fixing frames 3 and 3′. The distance between the twothickness regulating gaskets 4 may be adjusted in the range of 500 mm to1,300 mm. The thickness regulating gaskets 4 are made of a polymerictube with an outer diameter of 6 min to 40 mm such as a Teflon tube ornylon tube, a metal pipe with an outer diameter of 6 mm to 40 mm such asa stainless steel pipe, an aluminum pipe or a copper pipe, or asquare-shaped material with a height of 6 mm to 40 mm such as Teflon,nylon, rubber, stainless steel, aluminum, copper, etc. Preferably, thethickness regulating gaskets 4 are made of a Teflon tube or a nylon tubewith an outer diameter of 6 mm to 30 mm.

[0054] Subsequently, the lower carrier film 1 is disposed on the uppersurface of the lower horizontal heating plate 11, and both edges of thelower carrier film 1 are inserted into the carrier film fixture 13.Then, the lower carrier film 1 is continuously moved by driving thechain belt driving gear 134. The lower carrier film 1 is disposed on thelower surfaces of the thickness regulating gaskets 4. The lower carrierfilm 1 has a thickness of approximately 20 to 100 μm, and is made ofpolyethylene, polyester, polypropylene, polyvinyl alcohol, or etc.

[0055] The thickness regulating gasket-protecting film 8 surrounds theouter diameters of the thickness regulating gaskets 4, and movestogether with the lower carrier film 1. Here, the thickness regulatinggasket-protecting film 8 serves to protect the thickness regulatinggaskets 4 and promote the smooth transfer of the raw material compound,and is made of polyethylene, polyester, polypropylene, or polyvinylalcohol. The proper thickness of the thickness regulatinggasket-protecting film 8 is approximately 10 to 100 μm.

[0056] Subsequently, the upper carrier film 2 is disposed on the lowersurface of the upper horizontal heating plate 10, i.e., on the uppersurfaces of the thickness regulating gaskets 4, via the upper carrierfilm contact roll 7, and fixed to the carrier film fixture 13. Then, theupper carrier film 2 moves at the same rate as the lower carrier film 1.Here, the upper carrier film 2 has a thickness of approximately 20 to100 μm, and is made of polyethylene, polyester, polypropylene, polyvinylalcohol, or etc.

[0057] The raw material overflow prevention block 5 is installed on theapparatus of the present invention, thus preventing the raw materialcompound from flowing over the thickness regulating gaskets 4. The rawmaterial overflow prevention block 5 is made of a material with hightolerance to methyl methacrylate monomer and styrene monomer, andpreferably made of stainless steel or Teflon.

[0058] The upper horizontal heating plate 10 is moved downward using thevertically movable cylinders 9 so that the upper horizontal heatingplate 10 is located approximately 0.5 to 1.0 mm above the thicknessregulating gaskets 4. In case that the upper horizontal heating plate 10directly contacts the upper surfaces of the thickness regulating gaskets4, friction is produced on the interfaces between the upper horizontalheating plate 10 and the thickness regulating gaskets 4, thus causing adifficulty in moving the upper carrier film 2.

[0059] The height of the upper carrier film contact roll 7 is adjusteddepending on a desired thickness of the artificial marble plate to beproduced. Here, the contact roll 7 is not forcibly operated so that thecontact roll 7 is rotated only by the movement of the upper carrier film2.

[0060] The temperatures of the upper and lower horizontal heating plates10 and 11 are controlled according to the kinds of the used reactioninitiator so that the raw material compound can be heated in the rangeof approximately 30 to 100° C. The upper and lower horizontal heatingplates 10 and 11 are provided with a hot water heater, a steam heater oran electric heater unit as a proper heating source system. In anexemplary embodiment of the present invention, the upper and lowerhorizontal heating plates 10 and 11 are designed such that thetemperatures thereof are kept in the range of 75±5° C. using the hotwater heater.

[0061] After the above conditions of the apparatus are set, the chainbelt driving gear 13-4 is driven, and both edges of the lower and uppercarrier films 1 and 2 are inserted into the carrier film fixture 13.Then, the lower and upper carrier films 1 and 2 are continuously moved.The raw material compound from the raw material feed tank 6 is fed to agap between the lower carrier film 1 and the upper carrier film 2 viathe raw material overflow prevention block 5, and continuously hardenedby the lower and upper horizontal heating plates 11 and 10, thus beingproduced as an artificial marble plate.

[0062] Here, since the raw material compound is disposed on the gapbetween the lower carrier film 1 and the upper carrier film 2, air mustbe prevented from entering a space between the upper surface of the rawmaterial compound and the upper carrier film 2.

[0063] Hereinafter, with reference to test examples and comparativeexamples, the continuous producing of the artificial marble plate shownin FIG. 8 using the apparatus shown in FIG. 3 will be described indetail. The scope and spirit of the present invention are not limited bythe below examples.

TEST EXAMPLE 1

[0064] Methyl methacrylate (MMA) monomer in an amount of approximately75% by weight and polymethyl methacrylate (PMMA) polymer with a weightaverage molecular weight of not more than 10 in an amount ofapproximately 25% were mixed and dissolved to produce syrup with adesignated viscosity. Here, the viscosity of the produced syrup was 700cP. The measurement of the viscosity of the syrup was carried out using4 rotors in a Broock Field Viscometer in 30 rpm at 23° C. for 3 minutes.

[0065] Ethylene glycol dimethacrylate (“SR206” is a trademarkmanufactured by Sartomer Company, Inc., in U.S.) in amount ofapproximately 3% by weight as a crosslinking agent, sodium hydroxidewith an average particle size of 25 μm in an amount of approximately180% by weight, and benzoic peroxide in an amount of approximately 1% byweight as a reaction initiator were mixed with the above syrup in anamount of approximately 100% by weight within an agitator in whichvacuum degassing can be performed, and then the mixture was degassedunder the vacuum condition with a vacuum degree of less than 700 mmHgfor 10 minutes. As a result, a raw material compound with a viscosity of8,000 centipoise was produced. Then, the produced raw material compoundwas transferred into the raw material feed tank 6.

[0066] The thickness regulating gaskets 4 were set on the thicknessregulating gasket fixing members 3-1, and fixed to the thicknessregulating gasket fixing frames 3 and 3′. Here, the distance between thetwo thickness regulating gaskets 4 was 600 mm, and the thicknessregulating gaskets 4 was made of a Teflon tube with an outer diameter of13.0 mm.

[0067] Subsequently, the lower carrier film 1 was disposed on the uppersurface of the lower horizontal heating plate 11, and both edges of thelower carrier film 1 were inserted into the carrier film fixture 13.Then, the lower carrier film 1 was continuously moved by driving thechain belt driving gear 13-4. Here, the chain belt driving gear 13-4 wasdriven so that the linear velocity of the lower carrier film 1 wasapproximately 0.2 m per minute. The lower carrier film 1 was disposed onthe lower surfaces of the thickness regulating gaskets 4.

[0068] In order to protect the thickness regulating gaskets 4 andpromote the smooth transfer of the raw material compound, the thicknessregulating gasket-protecting film 8 surrounded the outer diameters ofthe thickness regulating gaskets 4, and was moved together with thelower carrier film 1.

[0069] The upper carrier film 2 was disposed on the lower surface of theupper horizontal heating plate 10, i.e., on the upper surfaces of thethickness regulating gaskets 4, via the upper carrier film contact roll7, and then inserted into the carrier film fixture 13 so that the uppercarrier film 2 was moved at the same rate as that of the lower carrierfilm 1.

[0070] The raw material overflow prevention block 5 was provided on theapparatus. The upper horizontal heating plate 10 was moved downwardusing the vertically movable cylinders 9, so that the upper horizontalheating plate 10 was located approximately 0.5 to 1.0 mm above thethickness regulating gaskets 4.

[0071] The above-prepared raw material compound from the raw materialfeed tank 6 was fed into a gap between the lower carrier film 1 and theupper carrier film 2 via the raw material overflow prevention block 5,so that the lower carrier film 1, the raw material compound and theupper carrier film 2 were continuously moved. Here, hot water wassupplied to the upper and lower horizontal heating plates 10 and 11 sothat the temperatures of the upper and lower horizontal heating plates10 and 11 were both 70° C.

[0072] The raw material compound was hardened by the above conditions,thereby being produced into an artificial marble plate with a thicknessof 13.0 to 14.0 mm. Here, the time required to harden the raw materialcompound was 30 minutes and the maximum reactive temperature wasapproximately 120 to 130° C. Properties of the obtained artificialmarble plate are shown in Table 1 below.

TEST EXAMPLE 2

[0073] The temperatures of the upper and lower horizontal heating plates10 and 11 were set to both 80° C. Other conditions were the same asthose of the test example 1.

[0074] Here, the required time was 23 minutes and the maximum reactivetemperature was approximately 130 to 140° C. Properties of an obtainedartificial marble plate are shown in Table 1 below.

TEST EXAMPLE 3

[0075] The temperatures of the upper and lower horizontal heating plates10 and 11 were set to both 90° C. Other conditions were the same asthose of the test example 1.

[0076] Here, the required time was 19 minutes and the maximum reactivetemperature was approximately 138 to 150° C. Properties of an obtainedartificial marble plate are shown in Table 1 below.

COMPARATIVE EXAMPLE 1

[0077] The temperature of the upper horizontal heating plate 10 was setto 70° C., and the temperature of the lower horizontal heating plate 11was set to 80° C. Other conditions were the same as those of the testexample 1.

[0078] Here, the required time was 25 minutes and the maximum reactivetemperature was approximately 130 to 135° C. Properties of the obtainedartificial marble plate are shown in Table 1 below.

COMPARATIVE EXAMPLE 2

[0079] The temperature of the upper horizontal heating plate 10 was setto 80° C., and the temperature of the lower horizontal heating plate 11was set to 70° C. Other conditions were the same as those of the testexample 1.

[0080] Here, the required time was 25 minutes and the maximum reactivetemperature was approximately 130 to 135° C. Properties of the obtainedartificial marble plate are shown in Table 1 below.

COMPARATIVE EXAMPLE 3

[0081] Properties of a commercially distributed acrylate artificialmarble plate were measured.

[0082] [Measurement of Properties]

[0083] Each of the obtained artificial marble plates by the testexamples 1 to 3 and the comparative examples 1 to 3 was precisely cutinto a section with a size of 550 mm×550 mm, and mounted on a bottomboard. Then, a bending degree of the cut section mounted on the bottomboard was measured in transversal and longitudinal directions using aclearance gauge. Here, a mark (+) denotes that the central portion ofthe cut section is convex relative to the edge portion of the cutsection, and a mark (−) denotes that the central portion of the cutsection is concave relative to the edge portion of the cut section.

[0084] Bending strengths of the plates were measured in accordance withASTM D 790. TABLE 1 Reactive temp.(° C.) Bending degree(mm) Upper LowerTransversal Longitudinal horizontal horizontal direction directionBending heating heating Initial After Initial After strength Divisionplate plate stage 7 days stage 7 days (kgf/mm) Test example 1 70 70 ±0.2±0.3 ±0.1 ±0.2 6.5 Test example 2 80 80 ±0.2 ±0.3 ±0.2 ±0.3 6.5 Testexample 3 90 90 ±0.4 ±0.5 ±0.3 ±0.4 6.4 Comparative 70 80 +3.0 +5.0 +2.0+3.0 6.5 example 1 Comparative 70 80 −2.0 −4.0 −2.0 −2.5 6.4 example 2Comparative Commercial product ±1.5 ±1.0 6.2 example 3 (n = 10)

[0085] As comparatively analyzing the above resulted values in Table 1,the transversal and longitudinal bending degrees of the artificialmarble plates according to exemplary embodiments of the invention (inwhich the same heat transmission manner was applied to the upper andlower surfaces of the raw material compound so that the upper and lowersurfaces of the raw material compound were set to the same temperature),were smaller than those of conventional artificial marble plates (whichwere obtained by applying the different transmission manners to theupper and lower surfaces of the raw material compound so that the upperand lower surfaces of the raw material compound were set to differenttemperatures). Further, the transversal and longitudinal bending degreesof the artificial marble plates according to exemplary embodiments ofthe invention were smaller than those of the conventional artificialmarble plates.

[0086] As a result, it is noted that the bending degree of a productobtained by hardening a raw material compound can be minimized byapplying the same heat transmission manner at the same temperature toupper and lower surfaces of the raw material compound.

[0087] While the conventional apparatuses shown in FIGS. 1 and 2 arelarge-sized so as to control the tensions of the one pair or two pairsof the steel belts and operate the steel belts, the apparatus of thepresent invention is advantageous in that the configuration andappearance thereof are relatively simple.

[0088] According to exemplary embodiments of the present invention, anapparatus and a method for producing an artificial marble plate applythe same heat transmission manner to upper and lower surfaces of a rawmaterial compound to be polymerized so that the hardening issimultaneously and uniformly performed on the upper and lower surfacesof the raw material compound, thus preventing the warpage of theobtained artificial marble plate. Further, since heat is directlytransmitted to the raw material compound using upper and lowerhorizontal heating plates, the apparatus of the present invention hasimproved productivity and heat transmission efficiency.

[0089] Compared with the conventional continuous hardening apparatuscomprising a pair of endless steel belts and other additionalcomponents, the apparatus of the present invention has a simpleconstitution, and minimizes the bending degree of the obtainedartificial marble plate. Further, compared with the conventionalcontinuous hardening apparatus comprising two pairs of endless steelbelts and other additional components, the apparatus of the presentinvention has a simple constitution, and minimizes the bending degree ofthe obtained artificial marble plate.

[0090] Although the preferred embodiments of the present invention havebeen disclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. An apparatus for continuously producing anartificial marble plate comprising: upper and lower carrier films facingeach other and receiving a raw material compound for the artificialmarble plate into a gap therebetween; upper and lower horizontal heatingplates, each including temperature controlling means and heating meansfor heating upper and lower surfaces of the raw material compound at thesame temperature by the same heat transmission manner to harden the rawmaterial compound, while the upper and lower carrier films moving alonga gap between the upper and lower horizontal heating plates; and a pairof gaskets disposed at horizontal edges of the upper and lower carrierfilms for regulating thickness and width of the artificial marble plateobtained by hardening the raw material compound.
 2. The apparatus forcontinuously producing an artificial marble plate as set forth in claim1, further comprising: upper and lower carrier film feed unwinders forfeeding the upper and lower carrier films to the gap between the upperand the lower horizontal heating plates; a raw material feed tank forfeeding the raw material compound for the artificial marble plate intothe gap between the upper and lower carrier films; a raw materialoverflow prevention block, disposed between the raw material feed tankand the lower horizontal heating plate, for preventing the raw materialcompound fed from the raw material feed tank from flowing over thegaskets; a contact roll, disposed after the raw material overflowprevention block and before the upper horizontal heating plate, forbringing the upper carrier film into contact with the raw materialcompound; a gasket-protecting film surrounding the gaskets to protectthe gaskets; gasket fixing members and a gasket fixing frame, disposedover the gaskets, for fixing the gasket; vertically movable cylinders,disposed on the upper horizontal heating plate, for controlling theheight of the upper horizontal heating plate; upper and lower carrierfilm recovery winders, communicated with end parts of the upper andlower horizontal heating plates, for collecting the upper and lowercarrier films from the artificial marble plate; and a cutting unit,communicated with the upper and lower carrier film recovery winders, forcutting the artificial marble plate released from the upper and lowercarrier films.
 3. The apparatus for continuously producing an artificialmarble plate as set forth in claim 1, further comprising a carrier filmfixture, disposed under the upper carrier film and on the lower carrierfilm, for fixing the upper and lower carrier films, for fixing the upperand lower carrier films.
 4. The apparatus for continuously producing anartificial marble plate as set forth in claim 3, wherein the carrierfilm fixture includes: a clamping pin; a chain belt for fixing theclamping pin; a position adjusting gear for adjusting the position ofthe chain belt; and a driving gear for driving the chain belt.
 5. Theapparatus for continuously producing an artificial marble plate as setforth in claim 1, wherein the heating means includes a hot water heater,a steam heater, or an electric heater unit.
 6. The apparatus forcontinuously producing an artificial marble plate as set forth in claim1, wherein the heating means heats the raw material compound at atemperature in the range of 30 to 100° C.
 7. The apparatus forcontinuously producing an artificial marble plate as set forth in claim1, wherein each of the gaskets is made of a circle-shaped orsquare-shaped tube or pipe.
 8. The apparatus for continuously producingan artificial marble plate as set forth in claim 1, wherein the outerdiameter or the height of each of the gaskets is 6 to 40 mm.
 9. Theapparatus for continuously producing an artificial marble plate as setforth in claim 1, wherein each of the gaskets is made of one materialselected from the group consisting of polymer and metal; and wherein thepolymer includes Teflon, nylon or rubber, and the metal includesstainless steel, aluminum or copper.
 10. The apparatus for continuouslyproducing an artificial marble plate as set forth in claim 1, whereinthe gaskets are disposed on the horizontal edges of the upper and lowerfilms with a space of 500 to 1,300 mm.
 11. The apparatus forcontinuously producing an artificial marble plate as set forth in claim1, wherein each of the upper and lower carrier films is made of one ormore materials selected from the group consisting of polyethylene,polyester, polypropylene and polyvinyl alcohol.
 12. The apparatus forcontinuously producing an artificial marble plate as set forth in claim1, wherein each of the upper and lower carrier films has a thickness of20 to 100 μm.
 13. The apparatus for continuously producing an artificialmarble plate as set forth in claim 2, wherein the vertically movablecylinders for controlling the height of the upper horizontal heatingplate are vertically moved by a distance of 0 to 1000 mm.
 14. A methodfor continuously producing an artificial marble plate comprising:feeding a raw material compound for the artificial marble plate to aspace defined by upper and lower carrier films facing each other and apair of gaskets disposed at horizontal edges of the upper and lowercarrier films; and heating upper and lower surfaces of the raw materialcompound at the same temperature by the same heat transmission manner toharden the upper and lower surfaces of the raw material compound at thesame rate, via a pair of upper and lower horizontal heating plates,while moving the upper and lower carrier films along a gap between theupper and lower horizontal heating plates.
 15. The method forcontinuously producing an artificial marble plate as set forth in claim14, wherein heating upper and lower surfaces of the raw materialcompound includes heating the upper and lower surfaces of the rawmaterial at the same temperature in the range of 30 to 100° C.
 16. Themethod for continuously producing an artificial marble plate as setforth in claim 14, wherein the raw material compound includes one ormore thermosetting resins selected from the group consisting ofunsaturated polyester resin, acrylate resin and methacrylate resin, oneor more fillers selected from the group consisting of aluminumhydroxide, calcium carbonate, silicate and magnesium oxide, one or morereaction initiators selected from the group consisting of peroxidecompound and perester compound, and acrylate compound as a crosslinkingagent.
 17. The method for continuously producing an artificial marbleplate as set forth in claim 14, wherein the raw material compound forthe artificial marble plate has a viscosity of 10 to 300 poise.
 18. Themethod for continuously producing an artificial marble plate as setforth in claim 14, wherein the upper horizontal heating plate is located0.5 to 1.0 mm above the gaskets.